One of the key requirements of a computer system is a place to store data. Typically computer systems employ a number of storage means to store data. One of the places where a computer can store data is in a disk drive which is also called a direct access storage device ("DASD").
A disk drive or DASD includes several disks which look similar to records used on a record play or compact disks which are used in a CD player. The disks are stacked on a spindle, much like several 45 rpm records awaiting to be played. In a disk drive, however, the disks are mounted to the spindle and spaced apart so that the separate disks do not touch each other.
The surface of each disk is uniform in appearance. However, in actuality, the surface of each disk is divided into portions where data is stored. There are a number of tracks of the disk situated in concentric circles like rings on a tree. Compact disks have tracks as do the disks in a disk drive. The tracks in either the disk drive or the compact disk essentially replace the grooves on a conventional record. Each track in a disk drive is further subdivided into a number of sectors which is essentially just one section of the circumferential track.
Disks in a disk drive are made of a variety of materials. Most commonly, the disk is made of metal or plastic. The materials from which the disk is made determines how data is stored on the disk. A plastic disk, such as those used as CDs, stores data using lasers and a laser is used to read the data back. Storage of data on a metal disk entails magnetizing portions of the disk in a pattern which reflects the data.
To store data on a metal disk, the metal disk is magnetized. In order to magnetize the surface of a disk, a small ceramic block which contains a magnetic transducer known as a write head is passed over the surface of the disk. More specifically, the write head is flown at a height of approximately six millionths of an inch from the surface of the disk and is flown over the track as the write head is energized to various states causing the track below to be magnetized to represent the data to be stored.
To retrieve data stored on a magnetic disk, a ceramic block which contains a read head is flown over the metal disk. The magnetized portions of the disk induce a current in the read head. By looking at output from the read head, the data can be reconstructed for use by the computer system.
Typically, the same ceramic block contains both a read head and a write head.
Like a record, both sides of a disk are generally used to store data or other information necessary for the operation of the disk drive. Since the disks are held in a stack and are spaced apart from one another, both the top and the bottom surface of each disk in the stack of disks has a ceramic block, also known as a slider, associated with each surface. This would be comparable to having a stereo that could play both sides of a record at once. In the record analogy, each side would have a stylus which played the particular side of the record.
Disk drives also have something that compares to the tone arm of a stereo record player. There are two types of actuators, rotary and linear. Rotary disk drives have a tone arm that rotates much like a record player. The tone arm of a rotary disk drive, termed a suspension assembly, typically has one slider attached at one end. The other end of a suspension assembly is attached to a comb-like structure. There is one suspension assembly associated with each surface of each disk. The comb-like structure facilitates holding the suspension assembly.
Like a tone arm, the suspension assembly rotates so that the read and write heads in the slider which is attached to the suspension assembly can be moved to locations over various tracks on the disk. In this way, the write heads can be used to magnetize the surface of the disk in a pattern representing the data at one of the several track locations or the read heads can be used to detect the magnetized pattern on one of the tracks of a disk. For example, the needed data may be stored on two different tracks on one particular disk, so to read the magnetic representations of data, the suspension assembly is rotated from one track to another track. A linear disk drive, by contrast, has a linear suspension assembly with a suspension assembly similar to that of a rotary disk drive. However, in a linear disk drive, instead of repositioning by rotation, repositioning is accomplished through linear movement.
Both the read head and the write head attached to the slider require a pair of wires to be attached to the slider itself. Thus, a typical suspension assembly has a total of four wires. These wires are very fine and are about 0.0014 inches thick, which is about half the thickness of a human hair. The wires carry electrical signals. The electrical signals attached to the write head are used to store representations of data on one of the disk surfaces of the disk drive. The electrical signals attached to the read head are used to carry signals representing the data back from one of the surfaces of the disk which has data stored on it. A set of wires for each read and write head are strung along each of the actuator arms in the disk drives. Each set of wires for each of the read heads and write heads typically is attached to a flexible cable which allows the suspension assembly to move while maintaining electrical connection with each of the heads on the slider.
In the past, attaching the fine wires to the read heads and the write heads, stringing the wire along the suspension assembly and attaching the wire to the flexible cable has been a very labor intensive process. The fine wires were attached to the head and strung along the actuator arm by human beings. Much of the work was done under a microscope, especially attaching one pair of fine wires to the read head and one pair of fine wires to the write head. The pairs of wire were also strung along the suspension assembly by humans. Finally, the fine wires are attached to the flexible cable by people.
The past procedure has many shortcomings. Many of the shortcomings stem from the labor intensive nature of attaching the wires to the heads and flexible cable and stringing the wire along the suspension assembly. Basically, the wires are very fine and small and the places to which the wires attach on the slider also are very small. The attachment typically is done by soldering the ends of the wires to a small pad. This is very exacting and detailed work and by its nature is very prone to human error.
For example, the flexible cable includes pads which are spots on the flexible cable to which the ends of the wires from the various heads are attached. Since there are so many wires that must be attached to the flexible cable, the pads are very small and closely spaced. There are many possibilities for error in attaching the wires to the pads on the flexible cable. Prior to attaching the wires to the pads on the flexible cable, the wires must be sorted. On a disk drive having eight disks there are sixteen surfaces most of which have both a read and write head associated therewith. Assuming each surface has both a read and a write element and four wires. There are 64 very fine wires that must be sorted and attached to very small pads. The sorting process is tedious and very prone to mistakes.
Even after successfully sorting the various wires, the wires are soldered to pads that are very closely spaced. Attaching the wires is also a source of mistakes. It is difficult for a human to consistently apply just the right amount of solder to a pad without having it flow to a closely spaced adjacent pad. When it does flow to an adjacent pad, a short occurs so the electrical signal will not pass through the wires to the write head or from the read head.
The same types of problems occur when attaching the wires to the various read heads and write heads on the slider. Problems also occur since the work is not done uniformly and with consistency. One person, for example, may have a knack for accomplishing the tasks while another may take along time to learn the skill. As a result, there are various levels of quality from person to person.
Other problems occur since the wires are so fine. For example, the wires can be crimped as it is sorted out which may result in a break in the electrical signals to or from the write or read elements on the slider.
As can be seen, there are many shortcomings associated with a human doing the task of attaching the wires to the head, stringing the wires along the suspension, twisting the wires for the purpose of noise suppression, sorting the wires and attaching them to the flexible cable where the wires terminate. This process seems prone to error, especially considering that the wires and pads upon which they are attached are very small. Because of the difficulty of this process as performed by humans, the time needed is high and as a result the labor costs are also high. The cost of the suspension assemblies are also increased in that more of the parts may be defective when compared to an automated process. Consequently, there is a need for a process by which the entire process of stringing the wires along the actuator arm, terminating the wires, and bonding of the slider to the suspension assembly can be automated.